The invention relates to a novel and unique memory device for directly and continuously storing information relative to partial pressure, or temperature, in an industrial process.
The invention relates more particularly to memory devices including, as storing element, material possessing magnetic domains.
Memory devices are classified as non-destructive and as destructive. Non-destructive memory devices afford the possibility to write and read then erase and again write information data. The destructive type can permit repetitive reading, but the information is permanently stored in the storing medium. A read only memory is typical of this second type.
Magnetic memory devices generally take advantage of the fixed orientation taken by magnetic moments under the effect of an external magnetic field, thus creating a magnetic condition in the material which can be read at a later time. In that sense, a magnetic memory device, in the prior art, is always non-destructive since a change of orientation of magnetic moments does not affect the fundamental structure of the material.
Read-only memory devices, nevertheless, have been manufactured in the past with such non-destructive memories by combining memory elements and by so separating electrically the zones of exposure to external influence that changes effected in one zone become irreversible in relation to another zone.
A common type of magnetic memory device is the magnetic tape used in sound recording or as an integral part of a computer. The magnetic tape in sound recording is not exposed directly to the effects of the acoustic waves. A transducer device is necessary in order to convert the acoustic wave into an electrical signal used to impress on the tape a corresponding magnetic field altering the magnetic state of the tape. With the electronic computer, data information is stored into the tape at the input side by electromechanical means, which also are in substance a transducer.
Attempts have been made already to apply the magnetic storing quality of magnetic materials to recording and monitoring of physical phenomena, and more particularly as a means for on-line chemical analysis of chemical reactions. For instance, in the U.S. Pat. No. 3,868,059 issued 2-25-75 to W. M. Hickam et al, assigned to the same assignee as the assignee of the present application, and entitled "Magnetic Bridge-Type Meter For Magnetically Permeable Particulate Matter", is described apparatus for the detection of fly ash emitted in the exhaust of a coal-fired furnace. The fly ash is admitted into the air gap of a permanent magnet associated with a magnetic bridge circuit and the change in inductance, thus caused, is detected as an indication of the operative conditions of the furnace. Therefore, the Hickam patent shows an apparatus having inherent magnetic characteristics which is directly exposed to an external physical phenomenon to be sensed and monitored, with the altered magnetic characteristics being used for detection and monitoring of the external physical phenemonon.
In the same vein, it is known from a paper presented at a Conference on Magnetic Materials held at Philadelphia in December 1975, entitled "Magnetic Gas Sensor" by Martin Rayl, Peter J. Woytowicz and Harold D. Hanson, to expose the core of an electromagnetic coil to oxidation-reduction reaction by gases, so that chemical changes occur in the material and the resulting change in inductance is measured as an indication of the presence of the gas.
Still, the prior art does not fulfill all the major needs of the industry regarding the acquisition of data relative to physical parameters in situ.
The present invention stems from the teachings set forth in the afore-mentioned copending Hickam patent application and proposes to expose a magnetic tape to a physical, or chemical agent, thereby to store into the material of the tape chemical changes which permanently affect the magnetic properties of the tape, and to sense such altered magnetic properties as an indication of the physical, or chemical, agent presence involved in such changes, as well as of process physical parameters involving such physical, or chemical agent.
The present invention is a novel approach to measuring temperature, or partial pressure, and storing information regarding such measured temperature or partial pressure as a function of time with respect to materials, industrial and chemical processing of materials, and/or physical phenomena.
One object of the present invention is to measure temperature, or partial pressure, in situ by storing chemical changes due to temperature in a selected material.
Another object of the invention is to store chemical changes, due to temperature, or partial pressure changes, into material exposed in situ to such changes as a function of time.
A further object of the invention is to provide material susceptible of permanent chemical changes which are indicative of a predetermined temperature level, or partial pressure level, reached under exposure.
Still another object of the invention is to measure temperature, or partial pressure, by sensing the magnetic properties of material exposed to temperature.
The present invention relates to a novel approach to measuring temperature, or partial pressure and storing such information as a function of time, in situ in the high temperature range, mainly from 500.degree. to 1600.degree. C.
The measurement of temperature is important for many industrial applications. Temperature reveals the progress of a thermal treatment and indicates physical as well as chemical changes imparted by heat or chemical reaction to a processed material, especially in the case of metal processing. Temperature is also an essential parameter indicative of the operative condition of a furnace.
The thermometer and the dilatometer are not applicable in a temperature range in excess of 200.degree. C. For very high temperatures, for instance the temperature of a furnace, temperatures have been measured by optical means responding to the spectrum of a light radiation emitting body. However, these are laboratory instruments which are costly, which require expertise in handling. Another drawback stems from the fact that the information gathered must be interpreted and is not directly storable. These instruments also are suitable only for extremely high temperatures and could not be used for measuring temperature of a black body.
There is a need for combining the precision of a scintillometer with the easy handling afforded by the conventional thermometer. In this regard, the invention can be used in situ within the confines of a high temperature furnace, gas, fluid or solid.
The present invention makes use of the property of certain chemical materials when exposed to a chemical agent having affinity therewith, to react in increasing proportion as a function of time of exposure, of the amount of chemical agent and/or of temperature. By a proper selection of the size and weight of the basic chemical material, knowing the precise conditions of exposure and duration thereof, the product of chemical reaction can be ascertained, and conversely, knowing the reaction product and all the parameters of the reaction except one, the latter can be known exactly by magnetic sensing.
The invention proposes to select solid material having stable physical and chemical characteristics at ambient temperature which, thus, can be used for storage of information, a quality which, for instance, conventional thermometers do not have.
The preferred physical parameter selected for characterizing the ultimate stage of the chemical reaction reached in the material is the magnetic properties, whereby by sensing a magnetic field, or measuring an inductance, an indication of the temperature having permanently modified the critical chemical composition of the material, e.g., of the maximum or minimum temperature experienced by the material, can be detected.